NEW DELHI (Reuters) - India’s financial crime fighting agency is investigating more than 100 “shell companies” that are suspected to be involved in the Punjab National Bank’s (PNBK.NS) near $1.8 billion fraud, a government source said on Tuesday.

The companies were allegedly used by Indian jewelers Nirav Modi and Gitanjali Gems’ Mehul Choksi to route funds, a source at India’s Enforcement Directorate told Reuters.

Modi and Choksi are at the center of the biggest ever bank fraud that has hit the country’s second largest lender Punjab National Bank. Both the businessmen have been accused of conspiring with bank officials to obtain advances for paying overseas suppliers.

A lawyer for Modi has denied any wrongdoing. Choksi’s firm has also said it has nothing to do with the fraud case.